Ultrasound imaging systems are generally known producing real-time images of internal portions of a tissue of a human body or the like. Such imaging systems include a multiple channel transmit beamformer and a multiple channel receive beamformer either coupled to a single array of ultrasonic transducers using a transmit and receive switch or coupled separately to a transmit transducer array and a receive transducer array. The transmit beamformer generates timed electrical pulses and applies them to individual transducer elements to generate an ultrasound beam to a portion of interest to be analyzed. A portion of the acoustic energy is scattered back towards the transducer array from the tissues structures. An array of received transducers, which may be the same as the transmit transducers converts the pressure pulses into corresponding electrical pulses. The receive beamformer usually has a plurality of processing channels with compensating delay elements, wherein a delay value for each channel is selected to collect ultrasound waves from a selected area of interest or from a selected steering direction.
A corresponding ultrasound receive beamformer with phased sub-arrays is e.g. known from U.S. Pat. No. 5,676,147.
The ultrasound penetration depth and, therefore, the area of interest is inversely proportional to the resonance frequency of the ultrasound waves, so that the field of view is close to the transducer array for high ultrasound frequencies. In order to provide high quality images of a field of view, fine and precise timing delays are required for these high ultrasound frequencies. Further, parasitic system-related time delays have an increased impact on the final image quality for these frequencies.
U.S. Pat. No. 4,790,320 discloses an apparatus for parallel processing of ultrasonic information to derive simultaneously multiple vectors of ultrasonic information per ultrasonic transmission. The apparatus includes in a transducer array for each transducer element an analog to digital converter and a delay processing subsystem associated with each analog to digital converter. The output of each first incremental delay means of all of the delay processing subsystems is applied to a first summing network and, simultaneously, the output of each of the second incremental delay means is applied to a second summing network which produces a second vector of time synchronized echo information.